How to Fix the 'Processing Instruction Target Not Allowed' Error in XSLT?

Processing Instruction Target Not Allowed: Resolved

The error "The processing instruction target matching 'xX[lL]' is not allowed" occurs in XSLT pages when the XML declaration is not placed at the very beginning of the file, preceding any other content.

Cause:

Xerces-based tools, including XSLT processors, produce this error when they encounter an XML declaration after encountering other content within the document. This includes:

• Visible content, such as spaces or tabs
• Invisible content, especially Byte Order Marks (BOMs)
• Stray XML declarations within the document

Solution:

To resolve this error, check for the following:

1. Visible Content:

Ensure there are no blank spaces or other visible content before the "" declaration. If any exist, remove them.

2. Invisible Content:

Use techniques recommended by the W3C (e.g., an XML parser or text editor) to identify and remove BOMs from the XML file.

3. Stray XML Declarations:

Search for "

Example:

In the provided XSLT page, the error occurs because the "" declaration is not placed before all other content:

By moving the XML declaration to the very beginning of the page, the error should be resolved:

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